1. Field of the Invention
The present invention relates to a vehicle behavior control apparatus having a longitudinal driving force distribution control, for controlling an engaging torque between front and rear shafts, and a braking force control for adding a braking force to a set wheel, the apparatus allowing these controls to be appropriately executed in cooperation with each other.
2. Description of Related Art
Japanese Patent Application Laid-Open (JP-A) No. 2002-46589 describes a vehicle having a longitudinal driving force distribution control for controlling an engaging torque between front and rear shafts and a braking force control for adding a braking force to a set wheel. In this apparatus, the braking control is inhibited while the connection state between the front and rear shafts is tight, even when a condition of starting the braking control by a brake control apparatus is established. On the other hand, during the execution of the braking control by the brake control apparatus, the braking control by the brake control apparatus is continued, even when the connection state between the front and rear shafts is changed to become tight, and the change in the connection state between the front and rear shafts is limited.
When the front and rear shafts are engaged with the vehicle in a head-out state during a turn, an understeer tendency' is increased by a difference of a lotus between the front shaft and the rear shaft (=difference in slip ratio=front-wheel-brake/rear-wheel-drive state). When the brake control is inhibited in this condition as in Japanese Patent. Application Laid-Open (JP-A) No. 2002-16589, a sufficient steering response cannot be expected. On the contrary, when the change in the longitudinal driving force distribution control is limited in a case where the brake control is executed earlier, as in Japanese Patent Application Laid-Open (JP-A) No. 2002-46589, a sufficient traction performance cannot be obtained. As described above, it is difficult to appropriately attain both the steering response and the traction performance only by switching the independent longitudinal driving force distribution control and the brake control.